Due to the increasingly stringent international limitations in terms of CO2 and NOx emissions imposed by ACARE FLIGHTPATH 2050 objectives and ICAO-CAEP standards, the development of new combustor concepts has become extremely important in order for aircraft engines to comply with these regulations. In this framework, lean-burn technology represents a promising solution and several studies and emission data from production engines have proven that it is more promising in reducing NOx emissions than rich-burn technology, especially at a high Operation Pressure Ratio (OPR).However, considering the drawbacks of this combustion strategy (flame stabilization, flashback or blowout or the occurrence of large pressure fluctuations causing thermo-acoustics phenomena) as well as the difficulties and the high costs related to experimental campaigns at relevant operating conditions, Computational Fluid Dynamics (CFD) play a key role in deepening understanding of the complex phenomena that are involved in such reactive conditions.Even though RANS approaches are very common in an industrial context since they can provide useful information in the preliminary design, scale-resolving methods are capable of providing high fidelity predictions in simulating reactive flows that feature strong unsteadiness and high levels of turbulence intensity. In this sense, hybrid RANS-LES models represent a good compromise between accurate prediction of flame behaviour and computational cost with respect to fully-LES approaches. Stress-Blended Eddy Simulation (SBES) is a new global hybrid RANS-LES methodology which ensures an improved shielding of RANS boundary layers and a more rapid RANS-LES “transition” compared to other hybrid RANS-LES formulations.In the present work, a full annular aeronautical lean-burn combustor operated at real conditions is investigated from a numerical point of view employing the new SBES approach using poly-hexcore mesh topology. The results are compared to experimental data and to previous numerical results obtained with Scale Adaptive Simulation formulation in order to underline the improvements achieved with the new hybrid RANS-LES formulation.

Scale Resolving CFD Investigations of Aerothermal Field and Emissions of a Lean Burn Aeroengine Combustor

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2021/volume/84898

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